Been playing on the onboard video for over a month now.

I have not been able to come to a decision on upgrading, thought I'd fish a little for suggestions.
Current Specs:
Intel Core 2 Duo E6550 2.33GHz
2 GB of RAM
Windows XP Pro
300W power supply
The problem I keep coming back to is the power supply. Are there any viable options without replacing it?
Or what would be a decent card for this setup assuming the PSU is upgraded also?
Thanks!
Comments
Test system specs were:
Intel Core 2 Extreme X6800
Asus Striker Extreme (Nvidia nForce 680i)
2x 1024 MB Corsair CM2X1024-6400
and the graphic card, obviously
Geforce 8800 GTS cards have been rebranded to 9800GT, so if you can't find one of them, you can look for the other.
PS: Just checked. You also have to make sure your PSU has an additional 6-pin power connector for graphic cards. The card requires more power than it can get via the PCIe bus, so if your PSU doesn't have one of those connectors, you may need to replace it after all.
If I may be so bold and make a suggestion: Get 2GB more RAM and Win7 x64, too.